Gear type hydraulic apparatus



May 17, 1955 o. NUBLING l 2,708,410

GEAR TYPE HYDRAULIC APPARATUS Filed Nov. 15, 1950 b VMWWM 2,?@3 ,4 i l) Patented May 1 7, 1 955 2,708,410 GEAR TYPE HYDRAULC AJPPARATUSl @tto Nbling, Berlin-Eroman, Germany Application November 15, 195i), Serial No. 195,713 8 Claims. (Cl. 10B-41) My invention relates to continuously regulable gear type hydraulic apparatus which may be either a pump or a motor. The hydraulic apparatus comprises an internally toothed outer ring gear wheel and an externally toothed inner gear wheel rotating with a small difference in angular velocity and mounted eccentrically with respect to each other.

One object of my invention is to provide an improved continuously regulable hydraulic drive apparatus of the type mentioned above by mounting one of the two eccen* trically arranged gear wheels movably in the direction of the eccentricity.

lt is a further obiect of my invention to provide an hydraulic apparatus in which said outer gear wheel is rigidly screwed to side walls which latter are mounted in slidably arranged bearings thus causing the gear wheels to bear against each other even when they are worn ofi, and have more play than the bearings.

It is a still further object of my invention to provide a hydraulic apparatus in which the working liuid is led into and out of the externally toothed inner wheel through a turnable control valve coaxially arranged with the same, and in which the quantity or oil passing through the hydraulic apparatus is regulated by rotating the control valve, thus reducing hydraulic frictional losses and oil leakage.

With these and other objects in view which will become apparent as the specification proceeds, my invention will be best understood by reference to the following specification and the illustrations in the accompanying drawings, in which:

Figs. l and 2 show respectively in longitudinal and transverse cross-section a regulable hydraulic apparatus according to the present invention;

Fig. 3 is a crosssection through the gear wheels and control valve maximum delivery; and

Fig. 4 is a cross-section through the gear wheels, and the control valve in a regulating position.

Similar letters refer to similar parts throughout the several views.

Referring now more specifically to the drawings there is shown an externally toothed inner wheel 1 and mounted by means of bearings 2, 3 in a housing 4 provided with a chamber 12, The externally toothed inner gear wheel 1 is provided with openings 10. Slots or ducts 11 and 13 are radially extending through the externally toothed inner wheel 1. An internally toothed outer ring gear wheel 5 is mounted eccentrically of the wheel 1 and rotates with the latter. In Fig. 3 a control valve 6 mounted in the inner gear wheel 1 coaxially therewith and turnably by a lever 7 is shown in the position for maximum delivery. The control valve 6 is provided with openings 14 at its right end as shown in Fig. l as well as with openings 34, 35 for controlling the supply and discharge of oil. The number of teeth in the inner wheel 1 is less by one than that of the outer ring gear wheel 5 and the teeth of the inner gear wheel abut tightly against the outer gear wheel, thus forming chambers 8 and 9.

During rotation in the direction of the arrow in Fig. 3 the volume of chambers 8 increases, and the volume of chambers 9 decreases.

The described hydraulic apparatus may serve as pump or motor. Since it has been found particularly advantageous to provide such pump with an adjustable control valve, the following description will refer to a pump, according to the present invention.

When the gear wheels are rotated in the direction of the arrow in Fig. 3 by a motor, not shown, chambers 8 become suction chambers, and chambers 9 pressure chambers. The suction chambers 8 communicate through slots 1l and port 3d with the suction space 6 of the control valve shown on the left of wall 36 in Fig. l, and pressure chambers 9 communicate with the pressure space 6 on the right of wall 36 through slots 13 and port 35 when the control valve is in the position shown in Fig. 3. The pressure space of the control valve communicates through opening 14 and annular chamber 14', with the outlet 14;". The suction space of the control valve communicate through opening 10 and chamber 12 in the casing 4 with the inlet 1.2. r1`he dimension a of the openings 34 and 35 corresponds to half the breadth of the slots 11 or 13, so that the chambers between the teeth are placed successively in direct connection with the suction space and the pressure space. In order to give high eiciencies even with worn wheels and high oil pressures, the outer wheel 5 is mounted, according to the invention, in bearings 36 which are movable in the direction of the eccentricity within the spaces 30', 36". The bearings are guided laterally by faces 31 in the housing 4. The outer wheel 5 is screwed rigidly to side walls 32, thus making possible to provide only one packing strip 33 on eac-h side. In order to relieve the control valve of load in the radial direction oil grooves 37 are arranged in the outer surface of the control valve 6. The grooves are of equal surface with the opening 35, they are connected to one another by means of bores, not shown, and are connected by bores 3S with the pressure space in the control valve. The pressure of the oil in grooves 37 counterbalances the pressure of the port 35.

The operation of a continuously regulable pump according to the present invention, described with reference to Figs. l to 4, is as follows:

A motor drives the externally toothed inner wheel 1 which is meshing with the internally toothed outer wheel 5 and takes it along. As the wheels rotate the control valve 6 is held stationary by the lever 7. Since the product of the volume of pumped oil multiplied by the pressure is constant, the pressure is a minimum when the delivered oil volume is a maximum. As shown in Fig. 3, the outer wheel is exposed to a pressure 15 due to the oil pressure in the spaces 9 and the inner wheel is exposed to a pressure 16. The arrangement of the teeth only permits a relative movement of the two gear wheels about the point 19 while the wheels rotate about axes passing through the points 17 and 18, respectively. The pressures 15 and 16 act directly on the bearings of the wheels 1 and 5 since the wheels cannot bear against one another in the direction of the forces 15'and 16.

These pressures on the bearings are however very small since the lowest oil pressures are associated with the highest deliveries. rIl`he motor driving the pump must overcome the resisting force 15 acting on the arm 2, the eccentricity of the two gear wheels.

If now the control valve 6 is rotated through an angle a, as shown in Fig. 4, then the chambers Z0 are connected to the suction space and the chambers 21 to the pressure space of the control valve. Consequently oil forced into the chamber 22 flows through the control valve back into the corresponding suction chamber and oil is sucked from the corresponding pressure chamber 3 into the suction chamber 25. Only a small quantity of oil is therefore delivered by the pump. Since the driving power and speed of revolution are constant the o1l pressure becomes considerably higher in accordance with the equation:

Oil delivery multiplied by oil pressure=constant.

The forces 26 and 27 produced by the pressure difference between the operating chambers have components 24 and 2S equal in magnitude to the forces 15 and i6.

It is known to arrange the play between the teeth so that it is smaller than the play in the bearings of the wheels. In this Way the component forces 28 and 29 extending in the direction of the eccentricity e do not act on the bearings but are taken up by the gear wheels abutting on each other. However, after the wheels have become worn, very large component forces 28 and 29 act on the bearings and result in a decrease in efciency. When the teeth of each gear wheel bear against the teeth of the other gear wheel this is not the case since both gear wheels rotate and the teeth slide upon one another at a speed which is considerably smaller than the speed of the supporting bearing faces.

ln an unregulated hydraulic apparatus the varying forces act always perpendicularly to the eccentricity and can therefore not be taken up by the gear wheels. This is not necessary if the hydraulic apparatus serves as motor, since large oil pressures in the oil motor always correspend to low speeds of rotation so that the eiiiciency remains approximately constant.

The loss due to liquid friction is very small at the packing strip 33 due to the small difference in the speeds of rotation of the outer and inner wheels.

Because of the small difference in the speeds of rotation of the two wheels loss of power due to friction is smaller than it would be if the oil pressure were taken up wholly by the bearings. By rigidly securing the outer wheel to side walls large sliding velocities which occur between rotating gear wheels and stationary side walls and cause high hydraulic friction are avoided, and oil leakage on both sides at the external and internal diarneters is reduced. The construction according to the invention is particularly advantageous as regards losses due to hydraulic friction since the side walls only slide upon the inner Wheel with a very low speed which is determined by the small difference in angular speeds between the two wheels. By causing the gear Wheels to bear against one another even when they are in worn condition, which is effected by the sliding of the bearings of the outer gear wheel, and thereby of the outer gear wheel itself in the direction of the eccentricity, the pressure of the oil is taken up by the gear wheels abutting on each other so that the eiciency determined by the friction of the teeth is not reduced.

The manner of using and applying the embodiment of my invention set forth above will be clear from the foregoing description. It is, of course, to be understood that my invention is not limited to the specific embodiment thereof here shown and described for purposes of illustration only. Various changes and modications may be made in the hydraulic apparatus set forth and in the structural details shown, without departing from the spirit of this invention.

What I claim is:

l. A hydraulic apparatus, comprising, in combination, a casing; a pair of spaced walls located in said casing and having parallel inner faces facing each other; a pair of rotary meshing gears one of said gears being mounted in the other, said gears being mounted in said casing between said Walls and having transverse end faces tightly engaging said inner faces of said walls, said walls and said meshing gears forming between each other a rst set of chambers increasing in volume during rotation and a second set of chambers decreasing in volume during rotation of said meshing gears, one of said gears being i formed with an axially extending inner chamber having a cylindrical inner surface and with radial ducts ending in circumferentially spaced orifices on said inner cylindrical surface and connecting said inner cylindrical surface with said chambers formed between said meshing gears; a tubular control valve turnably mounted in said casing and having an outer cylindrical surface slidably engaging said inner cylindrical surface of said one gear, said control valve having a transverse inner Wall dividing the interior of the same into a liquid receiving space and a liquid discharging space, said tubular control valve being formed with two arcuate ports connecting, respectively, said receiving space and said discharge space with said outer cylindrical surface of said control valve, said ports being arranged circumferentially spaced with respect to each other on either side of said transverse wall adjacent the same and between parallel transverse planes passing through said inner faces of said Walls, each of said arcuate ports extending over part of said orifices of said ducts for supply and discharge of liquid through the same, said tubular control valve being turnable from a normal maximum pumping position in which said receiving space communicates through the port associated therewith and through part of said ducts with said chambers increasing in volume, and said discharging space communicates through the port associated therewith and through other ducts with said chambers decreasing in volume during the rotation of said gears, to a minimum pumping position in which both said ports establish communication between said chambers increasing in volume with said chambers decreasing in volume through the interior of said tubular control valve; inlet and outlet means for a liquid communicating, respectively, with said receiving space and said discharging space in said control valve; and operating means for turning said control valve independently of the rotation of said rotary gears.

2. A hydraulic apparatus, comprising, in combination, a casing; a rotary outer ring gear rotatably mounted in said casing; a rotary inner gear rotatably mounted in said casing within said outer ring gear and meshing with the same, said outer ring gear and said inner gear having parallel axes of rotation and transverse end faces spaced the same axial distance; a pair of spaced transverse walls located in said casing and having parallel inner faces facing each other and tightly engaging said end faces of said gears, said Walls and said meshing gears forming between each other a first set of chambers increasing in volume during rotation and a second set of chambers decreasing in volume during rotation of said meshing gears, said inner gear being formed with an axially extending inner chamber having a cylindrical inner surface and with radial ducts ending in circumferentially spaced orifices on said inner cylindrical surface and connecting said inner cylindrical surface with said chambers formed between said meshing gears; a tubular control valve turnably mounted in said casing and having an outer cylindrical surface slidably engaging said inner cylindrical surface of said inner gear, said control valve having a transverse inner wall dividing the interior of the same into a liquid receiving space and a liquid discharging space, said tubular control valve being formed with two arcuate ports connecting, respectively, said receiving space and said discharge space with said outer cylindrical surface of said control valve, said ports being arranged diametrical with respect to each other on either side of said transverse wall adjacent the same and between parallel transverse planes passing through said inner faces of said walls, each of said arcuate ports extending over part of said orifices of said ducts for supply and discharge of liquid through the same, said tubular control valve being turnable from a normal maximum pumping position in which said receiving space communicates through the port associated therewith and through part of said ducts with said chambers increasing in volume, and said discharging space communicates through the port associated therewith and through other ducts with said chambers decreasing in volume during the rotation of said gears, to a minimum pumping position in which both said ports establish communication between said chambers increasing in volume with said chambers decreasing in volume through the interior of said tubular control valve; inlet and outlet means for a liquid communicating, respectively, with said receiving space and said discharging space in said control valve; and operating means for turning said control valve independently of the rotation of said rotary gears.

3. A hydraulic apparatus, comprising, in combination, a casing; a rotary outer ring gear rotatably mounted in said casing; a rotary inner gear rotatably mounted in said casing within said outer ring gear and meshing with the same, said outer ring gear and said inner gear having parallel axes of rotation and transverse end faces spaced the same axial distance; a pair of spaced transverse walls located in said casing and having parallel inner faces facing each other and tightly engaging said end faces of said gears, said walls being tixedly secured to said outer ring gear for rotation with the same, and slidably engaging the end faces of said inner gear, said walls and said meshing gears forming between each other a rst set of chambers increasing in volume during rotation and a second set of chambers decreasing in volume during rotation of said meshing gears, said inner gear being formed with an axially extending inner chamber having a cylindrical inner surface and with radial ducts ending in circumferentially spaced orifices on said inner cylindrical surface and connecting said inner cylindrical surface with said chambers formed between said meshing gears; a tubular control valve turnably mounted in said casing and having an outer cylindrical surface slidably engaging said inner cylindrical surface of said inner gear, said control Valve having a transverse inner wall dividing the interior of the same into a liquid receiving space and a liquid discharging space, said tubular control valve being formed with two arcuate ports connecting, respectively, said receiving space and said discharge space with said outer cylindrical surface of said control. valve, said ports being arranged diametrical with respect to each other on either side of said transverse wall adjacent the same and between parallel transverse planes passing through said inner faces of said walls, each of said arcuate ports extending over part of said orifices of said ducts for supply and discharge of liquid through the same, said tubular control valve being turnable from a normal maximum pumping position in which said receiving space communicates through the port associated therewith and through part of said ducts with said chambers increasing in volume, and said discharging space communicates through the port associated therewith and through other ducts with said chambers decreasing in volume during the rotation of said gears, to a minimum pumping position in which both said ports establish communication between said chambers increasing in volume with said chambers decreasing in volume through the interior of said tubular control valve; inlet and outlet means for a liquid communicating, respectively, with said receiving space and said discharging space in said control valve; and operating means for turning said control valve independently of the rotation of said rotary gears.

4. A hydraulic apparatus, comprising, in combination, a casing; a rotary outer ring gear rotatably mounted in said casing; a rotary inner gear rotatably mounted in said casing within said outer ring gear and meshing with the same, said outer ring gear and said inner gear having parallel axes of rotation and transverse end faces spaced the same axial distance; a pair of spaced transverse walls located in said casing and having parallel inner faces facing each other and tightly engaging said end faces of said gears, said walls being fxedly secured to said outer ring gear for rotation with the same, and slidably engaging the end faces of said inner gear, said walls and said meshing gears forming between each other a first set of chambers increasing in volume during rotation and a second set of chambers decreasing in volume during rotation of said meshing gears, said inner gear being formed with an axially extending inner chamber having a cylindrical inner surface and with radial ducts ending in circumferentially spaced orilices on said inner cylindrical surface and connecting said inner cylindrical surface with said chambers formed between said meshing gears; a pair of hollow tubular shafts, each tubular shaft being fixed on and projecting outwardly from one of said walls coaxial with said outer ring gear; bearing means supporting said tubular shafts, said bearing means being mounted on said casing slidable in a plane defined by the parallel axes of rotation of said outer ring gear and of said inner gear; a tubular control valve turnably mounted in said casing and having an outer cylindrical surface slidably engaging said inner cylindrical surface of said inner gear, said control valve having a transverse inner wall dividing the interior of the same into a liquid receiving space and a liquid discharging space, said tubular control valve being formed with two arcuate ports connecting, respectively, said receiving space and said discharge space with said outer cylindrical surface of said control valve, said ports being arranged diametrical with respect to each other on either side of said transverse wall adjacent the same and between parallel transverse planes passing through said inner faces of said walls, each of said arcuate ports extending over part of said oriiices of said ducts for supply and discharge of liquid through the same, said tubular control valve being turnable to a minimum pumping position in which both said ports establish communication between said chambers increasing in volume with said chambers decreasing in volume through the interior of said tubular control valve; inlet and outlet means for a liquid communicating, respectively, with said receiving space and said discharging space in said control valve; and operating means for turning said control valve independently of the rotation of said rotary gears.

5. A hydraulic apparatus as claimed in claim 4 wherein said tubular control valve is formed with a groove means on said outer cylindrical surface thereof arranged opposite the port associated with said receiving space in said control valve and having the same surface area as said port, said groove means communicating with said receiving space of said control valve so as to counterbalance the transverse pressure on said control Valve caused by said port.

6. A hydraulic apparatus, comprising, in combination, a casing, a rotary outer ring gear rotatably mounted in said casing; a rotary inner gear rotatably mounted in said casing within said outer ring gear and meshing with the same, said outer ring gear and said inner gear having parallel axes of rotation and transverse end faces spaced the same axial distance, said inner gear being formed with an axially extending inner chamber having a cylindrical inner surface, and with radial ducts ending in circumferentially spaced orifices on said inner cylindrical surface; a pair of spaced transverse walls located in said casing and having parallel inner faces facing each other, said transverse walls being iixedly secured to said outer ring gear for rotation with the same and slidably engaging the end faces of said inner gear, said transverse walls and said meshing gears forming between each other working chambers for an operating liquid communicating with said ducts; a pair of hollow tubular shafts, each tubular shaft being fixed on and projecting outwardly from one of said walls coaxial with said outer ring gear; bearing means supporting said tubular shafts, said bearing means being mounted on said casing slidable in a plane defined by the parallel axis of rotation of said outer ring gear and of said inner ring gear; inlet conduit means projecting from an end of said inner cylindrical chamber into the same and being provided with an arcuate supply port extending adjacent to said inner cylindrical surface of said inner gear opposite part of said orifices; and outlet conduit means projecting from an end of said inner chamber of said inner gear into the same and being provided with an arcuate discharge port also located adjacent to said inner cylindrical surface of said inner gear and opposite others of said orifices.

7. A hydraulic apparatus comprising, in combination, a casing including a pair of spaced walls having parallel inner spaces facing each other; a pair of rotary meshing gears one of said gears being mounted in the other, said gears being mounted in said casing between said walls and having transverse end faces tightly engaging said inner faces of said wall and axes extending normal to said end faces, said walls and meshing gears forming suction chamber means located on one side of a plane of symmetry through the axes of said meshing gears and increasing the volume during rotation, and pressure chamber means located on the other side of said plane of symmetry decreasing in volume during rotation of said meshing gears, one of said gears being formed with an axially extending cylindrical inner chamber having a cylindrical inner surface, and with radial ducts ending in circumferentially spaced orifices on said inner cylindrical surface, one part of said ducts connecting said inner chamber with said suction chamber neans, and the other part of said ducts connecting said inner chamber with said pressure charnber means; a control valve turnably mounted in said inner cylindrical chamber and including inlet conduit means projecting from one end of said inner cylindrical chamber into the same and being provided with an arcuate supply port extending adiacent to said inner cylindrical surface of said inner chamber, and outlet conduit means projecting from an end of said inner chamber into the same and being provided with an arcuate discharge port also located adjacent to said inner cylindrical surface of said inner chamber; and means for turning said control valve between a maximum pumping position in which said supply port is located on said one side of said plane of symmetry and opposite said orifices of said one part of said ducts, and said discharge port is located on the other side of said plane and opposite said orifices of said other part of said ducts, and a minimum pumping position in which both said supply port and said discharge port are located on both sides of said plane of symmetry and communicate with both said pressure and suction chamber means and establish connection between said pressure and suction chamber means for idle circulation of an operating liquid.

S. in a hydraulic gear purnp including two meshing pump gears, one of the pump gears being mounted within the other pump gear, in combination, a hollow gear body forming part of one of said pump gears and having an inner cylindrical surface, said hollow gear body being formed with radially extending ducts located in a transverse plane and connecting circumferentially spaced points of said inner cylindrical surface of said hollow gear body with exterior surface portions of said one pump gear for supplying and discharging, respectively, a liquid to the spaces between said pump gears; inlet conduit means projecting from an end of said hollow gear body into the same and being provided with an arcuate supply opening extending n said transverse plane of said ducts adjacent to said inner cylindrical surface of said hollow gear body; outlet conduit means projecting from an end of said hollow gear body into the same and being provided with an arcuatc discharge opening extending also in said transverse plane of said ducts adiacent to said inner cylindrical surface of. said hollow gear body spaced in circumferential direction from said supply opening, said inlet conduit means and said outlet conduit means being fixedly connected and turnable for adjusting the position of said supply opening and of said discharge opening' with respect to said radially extending ducts for varying the amount oi operating liquid supplied and discharged, respectively, through said inlet conduit means and said outlet conduit means, respectively; and means for turning said xedly connected outlet and inlet conduit means.

References Cited in the file of this patent UNlTED STATES PATENTS l,3ll,846 Gollings June l, 1920 1,660,464 Wilsey Feb. 28, 1928 1,682,393 Mohl Aug. 28, 1928 1,690,086 Miles Oct. 30, 1928 1,912,737 Svenson June 6, 1933 1,912,738 Svenson lune 6, 1933 2,011,338 Hill Aug. 13, 1935 2,148,282 Stevens Feb. 21, 1939 2,434,135 Witchger Jan. 6, 1948 2,445,967 Pigott et al. July 27, 1948 FOREIGN PATENTS 9,359 Great Britain of 1915 

